The present invention is directed to thioglycerol derivatives and their preparation, the derivatives having utility in optical materials such as lenses.
Plastic lenses for use in eyeglasses and cameras have become widespread in view of their lightweight, durability, dyeability and workability as compared to conventional glass lenses. Resin compositions suitable for the manufacture of optical lenses must possess certain characteristics, including a high refractive index, high surface accuracy, low dispersion properties and good heat resistance, impact resistance and scratch resistance. Diethylene glycol bis(allylcarbonate (DAC) and polycarbonates have conventionally been used for plastic lenses. Lenses made of DAC, however, have lower refractive indices than lenses made of glass of a corresponding overall thickness, and therefore do not perform as well in this regard.
U.S. Pat. Nos. 4,775,733 and 5,191,055 disclose polyurethane lenses made of a polymer between a xylylene diisocyanate compound and a polythiol compound having a higher refractive index than lenses made from DAC. However, such lenses generally suffer from poor heat resistance, hindering the ability to use high temperatures during heat treatment processing steps.
It therefore would be desirable to develop compositions for use in making optical materials that do not suffer from the various drawbacks mentioned above, and that have good machinability and processability.